Switching system for high-power radio-frequency energy



April 15 1952 Filed Jan. 7, 1949 W. H. SWITCHING SYSTEM FLARITY FOR HIGH-POWER 2 SHEETS-SHEET l Ilia K65\ PULSE I GENERATOR 62- 2 Tu.

OUTPUT B 68 i 63 I 63 7 22 l3 24 23' 24 I5 1'1 32 1o :4 29 4o 43 J O Ila :1, m,

OUTPUT A INVENTOR WARREN H. FLARITY A TTOR/VEY April 1952 w. H. FLARITY I 2,5,51

SWITCHING SYSTEM FOR HIGH-POWER RADIO-FREQUENCY ENERGY Filed Jan. 7, 1949 2 SHEETSSHEET 2 OUTPUT B INPUT OUTPUT A OUTPUT B INPUT OUTPUT A INVENTOR. WARR EN H. FLARITY ATTORNEY Patented Apr. 15, 1952 UNITED STATES PATENT 2,592,551 OF F ICE SWITCHING SYSTEM FOR HIGH-POWER RADIO-FREQUENCY ENERGY (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 9 Claims.

This invention relates to switching systems for radio-frequency energy and more particularly to switching systems for high-power radio-frequency energy which are operative at high speed in response to a control signal.

The present invention relates to a system for switching radio-frequency energy from one source to either one of two loads. The invention is therefore different from duplexer systems commonly employed in radars to permit the same antenna to be used for both transmitting and receiving. Duplexer systems normally include a gaseous transmit-receive tube which is made conductive by the high-power transmitted pulse but is unaffected by the received pulse. By contrast, the gaseous switch tubes employed in the system of the present invention are unaffected by high-power pulses of radio-frequency energy and are rendered conductive by a control voltage applied thereto at any desired time.

While the switching system of the present invention is suited for application in a great many ways, as will be apparent to those skilled in the art, it is particularly useful in a radar for the purpose of directing the output of a transmitter alternately to two antennas. In this way it is possible to greatly increase the directivity of a pulse signaling system.

It'is the general object of this invention to provide a switch for radio frequency energy, the switch being independently controlled and not affected by the presence or absence of the radio frequency to be switched.

It is another object to provide a radio frequency energy switch which is very fast acting and capable of switching energy from one output to another in a fraction of a micro-second.

It is a further object to provide a fast-acting switch for high-power radio frequency energy. These and other objects of the invention will be apparent to those skilled in the art from the following description of one form of the invention taken in connection with the accompanying drawings formin a part thereof in which:

Fig. 1 is a view of the exterior of the switch device.

Fig. 2 is a sectional view taken on the line 2 2 of Fig. 1.

Fig. 3 is a diagrammatic representation of the switch device when in condition to convey radiofrequency energy from the input to the output A.

Fig. 4 is a diagrammatic representation of the switch device when in condition to convey radiofrequency energy from the input to the output B.

Fig. 5 is an end view of a gaseous switch tube employed in the switch device.

Fig. 6 is a sectional view taken on the line 6-6 of Fig. 5.

Referring now in greater detail to the drawings, the switch device shown in Figs. 1 and 2. in

cludes an outer conductor [0 of complex configuration forming a cavity and having conventional terminals for connection with coaxial cables, there being an input terminal H, an output A terminal I2, and an output B terminal l3. An inner conductor l4 within the outer conduct tor it extends from the input terminal H to .the output B terminal 13 and is disposed coaxially within said terminals. The inner conductor I4 is physically maintained in coaxial relationship with the terminals I l and [3 by means of annular insulators 15 within the terminals. Conductor M is in part an input probe and in part a pick-up probe for output B.

An inner quarter wave length stub conductor it is connected at one end at H with the inner conductor l 4 to extend at right angles therefrom. As shown to advantage in Fig. 2, the outer conductor It] includes a stub portion l9 surrounding the inner stub conductor It and extending beyond the terminus 20 thereof. The end of the stub portion IQ of the outer conductor may be closed or left open as shown in the drawings since little or no radio-frequency energy will be present there. The stub conductor [6 is maintained in spaced relationship with the stub portion 19 of the outer conductor by means of an insulator l8.

A gaseous switch tube 22, which will be described in more detail in connection with Figs. 5 and 6, is mounted in an aperture in the stub portion H) of the outer conductor ID in such a way as to have its annular grid terminal 23 secured in contact with the outer conductor by means of clamps 24 and its plate terminal 25 connected to the terminus 20 of the inner stub conductor H5. The quarter wave length stub including outer conductor 19 and inner conductor 96 is terminated in an open circuit so as to reflect a short circuit to the junction I! with conductor I4 when the tube 22 is nonconductive. The stub is terminated in a short circuit so as to reflect an open circuit, so far as the stub is concerned, to junction I! with the conductor l4 when the tube 22 is conductive.

An enlarged portion of the outer conductor [0, hereinafter referred to as the resonator portion 28, provides a chamber wherein is mounted a quarter wave length resonant element 29 in parallel relationship with the inner conductor l4. The resonant element 29 is secured at one end as by soldering to the surface 30 of the resonator portion of the outer conductor. A second gaseous switch tube 32 is mounted in anaperture in another side 3! of the resonant portion 28 of the outer conductor in such a way as to have its annular grid terminal 33 secured in contact with the outer conductor by means of clamps 34, and its plate terminal 35 connected to the freeterminus 36 of the resonant element 29.

r A pick-up probe or conductor element. is a one end maintained coaxially in the output A terminal l2 by means of an annular insulator M. The other end of pick-up probe 40 extends into the resonator portion 28 of the outer conductor in parallel relationship with the resonant element 29, the pick-up probe 40 being on the side of the resonant element 29 opposite from the inner conductor M. The pick-up probe 43 may be in the form of a pick-up loop or may be, as shown in Fig. 2, connected to the side 3| of the outer conductor.

The resonant element 29 is preferably a quarter wavelength long and the distance between the sides 28 and 3| of the outer conductor is also substantially a quarter Wavelength. As shown in Fig. 1, the other dimension of the resonant portion 28 of the outer conductor i considerably less than a quarter wavelength. Having these dimensions, the resonant portion 28 cannot act as a waveguide and the end 43 thereof may be left open as shown in Fig. 2 without loss of radiofrequency energy. Alternatively, the end 43 may be closed.

The resonant element 29 should preferably be positioned equidistant from the inner conductor l4 and the pick-up probe 40, the physical spacing and dimensions being selected to provide the degree of coupling and frequency bandpass characteristics desired. When the gaseous switch tube 32 is non-conductive, the resonant element 29 is capable of receiving radio frequency energy from the inner conductor 14 and oscillating as a tuned circuit, there being created a standing wave on the element 29 with a high voltage condition at the terminus 3B. When the switch tube 32 is conductive, the terminus 36 cf the element 29 is grounded to the outer conductor and the element is incapable of sustaining oscillation at the fundamental frequency.

The identical gaseous switch tubes 22 and 32 shown in Figs. 1 and 2 are illustrated in detail in Figs. and 6 and are claimed per se in a copending application Serial No. 69,764, filed January '7, 1949, now United States Patent No. 2,553,569. The tube 22 comprises an annular metallic disk 23 having a central aperture 5|. An anode 52 is maintained coaxially in the aperture 5! by means of a coaxial vitreous cup 53 having its annular edge fused to the surface 54 of the disk 23.

A cylindrical metallic grid support 55 is mounted on the other fiat surface 56 of disk 23 in coaxial relationship with the aperture 5|. A wire mesh grid 51 is mounted on the support 55 so as to cover the open end thereof. A vitreous or metallic shell 58 is fused or sealed to the surface 56 of disk 23; the shell 58, disk 23 and cup 53 providing an air-tight envelope which is filled with a rare gas, such as argon, at a pressure of about 150 microns. Supporting wires 59 and 68 are fused in the shell 58 and carry a cathode 6| having an internal heater. Lead wire 62 is connected to the cathode BI and lead wires 62 and 63 are connected to the heater.

As shown in Figure 2, the leads 62, 62 of switch tubes 22 and 32 are connected by wire 65 to one terminal of a control signal generator 63. The other terminal of generator 66 is connected to the grids 51, 51 of tubes 22 and 32 through wire 61, outer conductor l0, annular metallic disks 23, 33, and grid supports 55, 55. Filament sources 68, 68 are connected to the leads B2 and 63 of each switch tube.

The switch tube 22 differs from the conventional gaseous triodes with a heated cathode in that the anode 52 may be exposed to high-power radio-frequency energy without ionizing the gas in the tube and rendering it prematurely conductive. The tube is fired solely by the application of a control signal between the lead 62 and disk 23 thereby impressing the signal across the cathode BI and grid 51. In this way the tube may be transformed from a non-conductive state to a conductive state within a space of time measured in fractions of a microsecond. When the tube is conductive, the anode 52 is placed in effective electrical connection with the annular disk 23.

It is characteristic of gaseous discharge tubes that an appreciable length of time, in the order of several microseconds, is required to complete deionization. In order to provide a radio-frequency switch device operable in an extremely short period of time, two switch tubes have been provided both of which are deionized initially when radio-frequency energy is directed to an output A of the switch. Then both switch tubes are simultaneously fired by an external signal and the energy is directed to an output B of the switch. This switching operation may be performed in a fraction of a microsecond. It will be apparent, for example, that if a pulse of radiofrequency energy in the order of six microseconds wide is applied to the input of the switch device and the switch tubes are energized in the middle of the pulse, the first half of the pulse will be directed to output A and the second half will be directed to output B.

Many useful applications of such a switch device will be apparent to those skilled in the art.

The operation of the switch device will now be explained with the aid of the diagrammatic representations shown in Figs. 3 and 4. Fig. 3 indicates the mode of operation when switch tubes 22 and 32 are nonconductive. Under these conditions the inner stub conductor l6, being a quarter wavelength long and having an open circuited terminu 20, reflects a short circuit to the junction I! with the inner conductor M. This effectively prevents radio-frequency energy from passing to output B terminal l3. The resonant element 29 is substantially a quarter wavelength long and is coupled with the inner conductor 14 so that energy applied to the input I is operative to maintain radio-frequency oscillations on the element 29. Pick-up element 40 is coupled to the resonant element 29 so that radio-frequency energy, represented by shade lines in the drawing, tends to flow from the input terminal II to the output A terminal l2.

Referring now to Fig. 4, when the gaseous switch tubes 22 and 32 are simultaneously fired, tube 22 short circuits the end 20 of stub l6 thus removing the short circuit from the junction IT with the inner conductor i4 and permitting energy to flow to output i3. At the same time, tube 32 connects the high voltage end of resonant element 23 to the outer conductor 28 thereby quenching the oscillations on the resonant element and preventing a flow of energy to output A terminal :2. Switching from output A to output B may be accomplished in a fraction of a microsecond. If the gaseous switch tubes 22,

2 are then deionized, the energy will again flow to output A. This latter switching operation may be performed in a few microseconds.

It is to be understood that while one embodiment of the invention has been described in considerable detail, this has been done for purposes of illustration and not by way of limitation. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the spirit of the invention and the status of the invention in the prior art.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A device for switching radio-frequency energy from a source to either of two loads comprising; direct coupling means between said source and one load, a resonant coupling means coupling said source by virtue of the resonance thereof to the other load, means connected to said direct coupling means for normally placing across said one load a low impedance relative to said one load to by-pass radio-frequency energy therefrom, switch means connected to said last named means operative upon actuation thereof to remove said low impedance, control means coupled with said resonant means for stopping the oscillations in same upon actuation thereof, actuating meansconnected to said switching means and said control means for simultaneously actuating same, whereby the energy is switched from one load to the other load.

2. A switch for radio-frequency energy comprising a conducting surface shaped to form the bounding walls of a cavity, an input terminal to said cavity and a pair of output terminals A and B to said cavity, a first conductor within said cavity connecting the input terminal with the output terminal B, a second conductor also located within said cavity connected to a point on said first conductor and forming with said conducting surface a transmission line section which is normally operative to reflect a low impedance across said first conductor and said conducting surface whereby to bypass energy from said output terminal B when radio-fremeans when said device is actuated, a second output including a second output terminal con'- nected to a pick-up element in said cavity which first output terminal.

' 4. A device for switching radio-frequency energy from a source to either of two loads comprisdirect coupling means connecting said source and one load, resonant coupling means connecting said source by virtue of the resonance thereof to the other load, switching means connected to said direct coupling means for periodically placing and removing across said one load a low impedance relative to saidone load to periodically by-pass radio-frequency energy therefrom, control means coupled with said resonant means for periodically stopping the oscillations in same, actuating means connected to said switching means and said control means for actuating same, whereby the energy is peri odically switched from one load to the other load.

5. A switch for radio-frequency energy comprising a conducting surface shaped to form the bounding walls of a cavity, an input terminal thereto, and output terminals A and B, a first conductor within said cavity connecting the input terminal with the output terminal B, a second conductor also located within said cavity connected to said first conductor near said terminal B and formin with said conducting surface a transmission line section which is normallyopquency energy is fed between said input terminal and another point on said conducting surface, a resonant element within said cavity coupled to said first conductor, a pick-up probe within said cavity physically separated from but electrically coupled between said resonant element and said output terminal A, and switch means operable simultaneously to remove the low impedance reflected by said transmission line section and to detune the resonant element. whereby the radio-frequency is switched from the output terminal A to the output terminal B.

3. A radio-frequency switch comprising a coaxial line having an input terminal for connection to a source, the inner conductor of said line connecting to a first output terminal, a portion of the outer conductor of the line bein enlarged to form a cavity between said input terminal and the said first output terminal, impedance reflecting means including an electron conduction switch device connected across a transmission line section which consists of a first conductor connected to the said inner conductor of said coaxial line at a point within said cavity, and a portion of said outer conductor so as to reflect a small impedance across said coaxial line in the vicinity of said first output terminal when said device is quiescent and to reflect a large impedance when said device is actuated, resonant means within said cavitycoupled to said coaxial line, a second electron conduction.

switch device connected to said resonant means to cause oscillations to cease in said resonant erative to reflect a low impedance across said first conductor and said conducting surface whereby to bypass energy from said output terminal B when radio-frequency energy is fed between said input terminal and another point on said conducting surface, a resonant element within said cavity coupled to said first conductor, a pickup probe within said cavity physically separated from but electrically coupled between said resonant element and said output terminal A, and switch means operable to remove the low impedance reflected by said transmission line section and to detune the resonant element,

whereby the radio-frequency is switched from the output terminal A to the output terminal B,

6. A radio-frequency switch comprising a co axial line having an input terminal for connection to a source, the inner conductor of said line connecting said input terminal to a first output terminal, a portion of the outer conductor of the line being enlarged to form a cavity between said input terminal and the said flrst output terminal, impedance reflecting means including an electron conduction device connected across the a transmission line section which consists of a first conductor connected to the said inner conductor of said coaxial line and a portion of said outer conductor, said transmission line operative to reflect a small impedance across said coaxial line in the vicinity of said first output terminal when said device is quiescent and to reflect a large impedance when said device is actuated, resonant means within said cavity coupled to said coaxial line, a second electron conduction device means connected to said resonant means to cause oscillations to cease in said resonant means when said device is actuated, a second output including a second output terminal connected to a pick-up element in said cavity which is physically separated from but electrically coupled to said resonant means swam whereby when both said devices are actuated the energy will be switched from said second to said first output terminal. Y

'7. A radio-frequency switch comprising a coaxial line having an input terminal for connection to a source, the inner conductor of said line connecting said input terminal to a first output terminal, a portion ofthe outer conductor of the line being enlarged to form a cavity between said input terminal and thesaid first output terminal, impedance reflecting means including an electron conduction device connected across a transmission line section which consists of a first conductor, connected to the said inner conductor of said coaxial line, and a portion of said outer conductor operative to reflect a small impedance across said coaxial line in the vicinity of said first output terminal when said device is in a given state of conduction, and to reflect a large impedance when said device is in another state of conduction, resonant means within said cavity comprising a probe connected at one end to said outer conductor, said probe being parallel to a portion of said inner conductor and an odd number of quarter wave lengths long, a second electron conduction switch device connected between the other end of said probe and a point on said outer conductor to cause oscillations to cease in said probe when said device is in given state of conduction, a second output including a second output terminal connected to a pick-up element in said cavity which is coupled to said resonant means whereby when said devices are simultaneously actuated the energy will be switched from one output terminal to the other output terminal.

8. A combination for switching energy of a given frequency from a source of such energy to either of two loads comprising a first means coupling said source to one of said loads, a second means coupled across said one load for normally shunting same with a low impedance tobypass said energy therefrom, said second means including a first gaseous discharge device having states of conduction and non-conduction and which removes said low impedance from across said one load to allow said energy to flow thereto in only one of said states of conduction, resonant circuit coupling means tuned to said given frequency for coupling said source to the other of said loads by virtue of the resonance thereof, a circuit coupled to said resonant circuit including a gaseous discharge device having states of conduction and non-conduction for detuning same during only that state of conduction which corresponds to the state of conduction of said first gaseous discharge device which removes said low impedance from across said one load, the detuning of said resonant circuit resulting in cessation of flow of said energy to said other load, means coupled to said gaseous discharge devices for alternately and simultaneously switching same into a similar state of conduction and non-conduction whereby .the said energy is switched from one load to the other.

9. A combination for switching radio-frequency energy of a given frequency from a source of such energy to either of two loads comprising a first means coupling said source to one of said loads, a transmission line sector coupled across one of said loads, a first gaseous discharge device means having states of conduction and nonconduction coupled across said transmission line sector operative in conjunction with said transmission line sector to reflect a low impedance across said one load to by-pass the energy there from in only one of said states of conduction, a 1 second transmission line sector having a resonant length at said given frequency operatively coupled between said source and the other of said loads for coupling energy therebetween by virtue of the resonance thereof, a second gaseous discharge device means having states of conduction and non-conduction coupled across said transmission line sector operative to detune same during only the state of conduction corresponding to that state of conduction which corresponds to the state of conduction of said first gaseous discharge device wherein said low impedance is not reflected across said one load, the detuning of said resonant circuit resulting in cessation of flow of said energy to said other load, means coupled to said gaseous discharge devices for alternately and simultaneously switching same into a similar state of conduction and non-conduction whereby said energy is switched from one load to another.

WARREN H. FLARITY.

REFERENCES CITED -The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,189,549 Hershberger Feb. 6, 1940 2,404,832 Espley July 30, 1946 

